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Why are my even motors working harder than the odds?

Discussion in 'Cinestar 8' started by Steve Maller, Feb 14, 2013.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    I am really pleased with the stability and smoothness of my CS8, and my camera balancing is also improving to the point where my videos are coming out super smooth.

    However, I'm really digging deep to understand how to make the copter as safe, reliable and performant as I can, so I keep examining all the data I get from the various sources. And this one has me stumped. I looked at my GPX file from a recent very uneventful flight in my backyard, and I see that my even motors seem to be working quite a bit harder than the odd ones. Now, to be fair, I was slowly rotating the copter for about 10% of the flight, but that would seem to me to not necessarily indicate these numbers.

    I just checked my mx20 trims, and they're all dead center. The copter and gimbal are balanced, and I calibrated the ACC and gyros before I flew. I have not calibrated the compass lately, but I was flying in pure manual mode (no PH or AH), so I can't imagine that was an issue.

    Any thoughts? I've attached the GPX file and a graph of both the current and temperature data. Very weird...

    The only extenuating circumstance is that it was very foggy, and there was a good deal of moisture on the booms when I landed (just beneath the props). The rest of the copter was dry.

    temps.jpg Amps.jpg
     

    Attached Files:

  2. Gary Haynes

    Gary Haynes Administrator
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    Steve my take is that it looks pretty normal. Most of my files have similar characteristics. You would think that if everything was perfect that they would be grouped together more tightly. But just hasn't been my experience in the past.

    I grabbed one at random.

    Screen Shot 2013-02-14 at 12.08.31 PM.png
     
  3. Steve Maller

    Steve Maller UAV Grief Counselor

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    Thanks for doing that, Gary.

    After I posted this, I got to thinking that I should check my motor alignment. I bet that one motor (or prop or boom) that's slightly out of vertical or a single bearing that's going bad could cause this. But if others see similar numbers, maybe it's a red herring. I am going to go back over some of my older GPX files (I save them all) and see if a pattern develops.
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yeah, all it takes is one motor that's imparting a yawing vector and the other group has to work to counteract it.

    Andy.
     

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